The present invention relates to nanoporous granular materials, and more particularly, to a process for producing a starting material in a granular form and in a nanoporous anhydrous state, a process for improving the water-solubility and controlled release characteristics of a detergent material, and a detergent composition.
Starting materials in the granular form, such as those used for making detergent compositions, have various disadvantages related to the lack of particle size and particle pore size uniformity. One major disadvantage resulting from granular materials having non-uniform pore size, low porosity and non-uniform size distribution is that the solubility of the detergent composition in water is detrimentally affected. Currently, detergent formulators are faced with numerous problems which impede delivering the active ingredients to the fabric or dishware to be cleaned. By way of example, recent low dosage or xe2x80x9ccompactxe2x80x9d detergent products experience dissolution problems, especially in cold temperature laundering solutions (i.e., less than about 30xc2x0 C.). More specifically, poor dissolution results in the formation of xe2x80x9cclumpsxe2x80x9d which appear as solid white masses remaining in the washing machine or on the laundered clothes after conventional washing cycles. These xe2x80x9cclumpsxe2x80x9d are especially prevalent under cold temperature washing conditions and/or when the order of addition to the washing machine is such that the laundry detergent is added first, the clothes are added thereafter and the water is added in the end, commonly known as the xe2x80x9cReverse Order Of Additionxe2x80x9d or xe2x80x9cROOAxe2x80x9d. Similarly, this clumping phenomenon can contribute to the incomplete dispensing of detergent in washing machines equipped with dispenser drawers or in other dispensing devices, such as a granulettes. In such cases, the undesired result is undissolved detergent residue in the dispensing device.
Another disadvantage is that non-uniform granular materials for detergent applicants do not have a high amount of liquid loading capability, which is necessary, for example, for loading perfume onto a detergent granule. Also it has been recognized by the inventors of this invention that larger pore size and non-uniform pore size distribution in a granular detergent composition leads to lower active agglomerates, i.e., agglomerates that do not have the level of activity desirable for detergent applications.
Another disadvantage of this particle size non-uniformity in powdered starting materials is the presence of sometimes significant amounts of very fine particles which very frequently lead to safety and health problems due to the risk of dusting and pollution by these very fine particles. Consumers of detergent compositions do not want to be exposed to detergent agglomerates that have these undesirable dusting characteristics. Another problem in the detergent area is that the non-uniform size caused the granular starting materials to generally flow with difficulty, which makes it difficult to handle them and in particular, to dose them correctly during usage.
It is very desirable to produce starting materials, such as detergent materials, in the form of granules, that is to say, agglomerates of powder grains having a regular shape, an even surface, a nanoporous sized porosity, and of a generally graded size. The desirability of creating nanoporous sized granular starting materials for laundry and cleaning applications, such as in detergent compositions has been recognized by the inventors of this invention and it has been their focus to develop a process and product that results in granular materials that dissolve easily, are high active agglomerates and that have high liquid loading capability. It has been recognized that in the non-detergent applications, these nanoporous sized granules, which are less volatile than particles of powder, exhibit an appreciably reduced risk of atmospheric pollution and consequently of poisoning by inhalation via the respiratory tract, in the case of toxic starting materials. Further, when the starting material is provided in the form of granules having a regular shape, an even surface and a graded size, it can easily be handled, especially owing to ease of flow, and in particular it is easy to carry out the precise automatic weighing thereof for packaging purposes as well as dosing during subsequent uses. The present invention overcomes the problems, as set forth above.
Lyophilization is a known technique for obtaining anhydrous products which comprises the desiccation, by sublimation, of a product which has been solidified beforehand by freezing. This lyophilization is used for the manufacture of pharmaceutical, cosmetic, food or veterinary products in pulverulent form.
Published Japanese Patent Application JP 87 305 829 describes the preparation of a chitosan powder by dissolving chitosan in an acid, suspending, freezing and lyophilizing in order to obtain chitosan granules. Such a process does not make it possible to obtain granules with an even surface and with a homogeneous size, and in the nanoporous pore size range.
Published Japanese Patent Application JP 81 152 449 describes a process for the production of a fine powder which consists in dissolving a vehicle substance in an alcoholic solvent, in spraying the solution in an atmosphere at a temperature of less than xe2x88x9240 degrees C. in order to obtain frozen granulated fines and in drying the granules under vacuum while retaining them in the frozen state. Owing to the fact that the granules are formed by spraying by means of a propellant gas, the flow obtained is in the form of a more or less continuous thin stream and it is not possible to obtain frozen granules of homogeneous size, nor are they nanoporous.
U.S. Pat. No. 5,611,973 issued to Gurfein et al. on Mar. 18, 1997 discloses a process for producing a starting material, and in particular colouring materials, in the form of anhydrous granules having a regular shape, an even surface and a graded size. This process provides granules having sufficient cohesion for their subsequent uses and provides granules having a microporous structure which facilitates subsequent dissolution of the product. However, this patent does not provide a process for producing nanoporous size granular starting materials that have markedly improved solubility, activity, liquid loading capability and particularly, nanoporous granular materials for detergent applications.
The invention meets the needs above by providing a process for producing a starting material in a granular form and in a nanoporous anhydrous state, a process for improving the water-solubility and controlled release characteristics of a detergent material, and a detergent composition.
In one aspect of the present invention, a process for producing a starting material in a granular form and in a nanoporous anhydrous state is disclosed. The process includes the steps of obtaining a starting material in a form of a dispersion or solution in a sublimable solvent or mixtures of sublimable solvents, forming graded droplets by atomization, freezing the graded droplets in a freezing medium at a controlled freezing rate of at least 100xc2x0 C. per second to form frozen droplets and drying the frozen droplets by vacuum sublimation to obtain freeze-dried granules of the starting material in a nanoporous anhydrous state. The starting material in dispersion or solution form has a viscosity suitable for atomization and formation of graded droplets.
In another aspect of the present invention, a process for improving water-solubility and controlled release characteristics of a detergent material is disclosed. The process includes the steps of obtaining a detergent starting material in a form of a dispersion or solution in a sublimable solvent or mixtures of sublimable solvents, forming graded detergent droplets by atomization, freezing the graded detergent droplets in a freezing medium at a controlled freezing rate of at least 100xc2x0 C. per second to form frozen detergent droplets, and drying the frozen droplets by vacuum sublimation to obtain freeze-dried detergent granules of the detergent starting material in a nanoporous anhydrous state. The detergent starting material in dispersion or solution form has a viscosity suitable for atomization and formation of graded droplets.
In yet another aspect of the present invention, a detergent composition comprising freeze-dried detergent granules in a nanoporous anhydrous state having uniformly sized pores having a pore size less than about 300 nanometers is disclosed.
These and other objects, features and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the preferred embodiment and the appended claims.
In the preferred embodiment of the present invention, the process for producing a starting material in a granular form and in a nanoporous anhydrous state includes the step of obtaining a starting material in a form of a dispersion or solution in a sublimable solvent or mixtures of sublimable solvents. The starting material can be provided directly in the form of a solution or of a dispersion in a suitable solvent or mixture of solvents, the viscosity of which can optionally be adjusted by the addition of a chemical agent or by the variation in a physical parameter, such as the temperature or the concentration of solid material. If the starting material is provided in the form of an anhydrous powder, it is then necessary to prepare a solution or dispersion of this powder in a suitable solvent or mixture of solvents.
The solutions or dispersions of the starting material used in the process according to the invention are obtained simply by dissolving or dispersing the powder in a solvent or mixture of solvents suitable for lyophilization. Suitable solvents for lyophilization include water, isopentane, dimethyl sulphoxide, methylamine, ethylamine, diethylamine, propylamine, fumaric acid, acetic acid, t-butyl alcohol, t-amyl alcohol, 1,4-dioxane, isobutane, ethylene oxide and cyclohexane. Water is the preferred sublimable solvent.
The solutions and dispersions used in the process of the invention must have a viscosity such that they can be formed into graded droplets by atomization. The atomization can be accomplished by ultrasonic, acoustic, electrostatic means, pressure swirl nozzles or two-fluid nozzles, the preferred mode being ultrasonic atomization.
Consequently, the starting material in the form of dispersion or solution has a viscosity desirably in a range of from about 1 cP to about 250 cP at a solution temperature in a range of from about 60xc2x0 C. to about 91xc2x0 C. and at a shear rate in a range of from about 1000 secxe2x88x921 to about 10000 secxe2x88x921, preferably in a range of from about 25 cP to about 125 cP and more preferably in a range of from about 50 cP to about 100 cP. The term xe2x80x9csolution temperaturexe2x80x9d means the temperature of the solution or dispersion of the starting material.
In the preferred embodiment, a structuring agent is added to the starting material in dispersion or solution to affect crystal growth formation in the graded droplets during the step of freezing. Mention may be made, among the structuring agents which can be used in the solutions or dispersions according to the invention, of mannitol, glucose, lactose, maltose, polyethylene glycol, starch, polyvinylpyrrolidone, inorganic salts, sorbitol and CARBOPOL(trademark) brand carboxyvinyl polymer (Goodrich Chemical Co.). The choice of the structuring aid will very clearly depend on the subsequent use envisaged for the granules. The amount of additives can be easily determined by a person skilled in the art and depends on the additive.
In the preferred embodiment of the present invention, the starting material in dispersion or solution form has a viscosity suitable for atomization and formation of graded droplets. It is sometimes necessary to add one or a number of additives in order to obtain the aforementioned viscosity which makes it possible mechanically to form graded droplets by atomization and/or to confer a certain cohesion or degree of binding on the resultant granules. These additives are generally chosen from the gelling agents known in lyophilization. Suitable gelling agents which can be used in the solutions or dispersions according to the invention, include carbomers, hydroxyethyl cellulose, carboxymethyl cellulose, agar, xanthan gum, starch, polyethylene glycol, polyvinylpyrrolidone, locust bean gum, guar gum, gelatin, casein, pectin, alginates and carrageenates. It is also possible to adjust the viscosity of the solution or of the dispersion by adjusting the temperature of the solution or of the dispersion during the atomization step or even by adjusting the percentage of solids in the solution or in the dispersion.
In the preferred embodiment of the present invention, the process for producing a starting material in a granular form and in a nanoporous anhydrous state includes the step of forming graded droplets by atomization. A significant aspect of the process of the present invention relates to the formation of drops of graded size from the solution or dispersion of the starting material. This stage is a mechanical shaping stage which, in contrast to other techniques such as spraying or manifold of pipes or needles for droplet formation, makes it possible to obtain drops with a well-defined generally spherical or semi-spherical, shape, an even surface and a finely graded size. By using atomization techniques, such as by ultrasonic, acoustic, electrostatic, pressure swirl nozzle or two-fluid nozzle means, the preferred mode being ultrasonic atomization, it is possible to form graded droplets which have a uniform shape and size. Desirably, the graded droplets have a uniform spherical shape and a size in a range from about 10 xcexcm to about 700 xcexcm, and preferably they have a uniform spherical shape and a size in a range from about 20 xcexcm to about 100 xcexcm. The drops formed can comprise starting materials of different chemical natures and thus form a starting material in the form of granules having the characteristics of each of the starting materials.
In the preferred embodiment of the present invention, the process for producing a starting material in a granular form and in a nanoporous anhydrous state includes the step of freezing the graded droplets in a freezing medium at a controlled freezing rate of desirably at least 100xc2x0 C. per second to form frozen droplets. Preferably, the controlled freezing rate is at least 200xc2x0 C. per second, and more preferably, the controlled freezing rate is at least 400xc2x0 C. per second. The inventors have discovered that this step is the most critical step to achieving nanoporous sized granular starting materials, i.e., the carefully controlled and preselected rate of cooling. Without being bound to any specific theory, it is believed that at cooling rates of at least 100xc2x0 C. per second, the water which usually forms ice-crystals at low freezing rates, such as rates less than about 100xc2x0 C. per second, now either forms very small crystals, or becomes frozen in its glassy state. As a result of this first phenomenon, when water is sublimed from the frozen matrix in a vacuum oven, a highly porous matrix is left behind with pores of a size similar to those of the frozen water pockets that are formed during the freezing process. These pores are not only small and nanometer sized, but also have a very homogeneous size distribution. In the preferred embodiment of the present invention, the freeze-dried granules in a nanoporous anhydrous state have uniformly sized pores having a pore size less than about 300 nanometers.
Without being bound to any specific theory, it is believed by the inventors that any salts that are soluble in water and that crystallize out of the solution during freezing, form either micron or submicron, and more particularly, nanometer sized crystals during the fast rates of freezing, such as rates of at least 100xc2x0 C. per second. As a result of this second phenomenon, when the water is sublimed from the frozen matrix, a nanometer sized crystalline agglomerate having a size substantially equal to the original droplet size is formed. The inventors believe that it these two phenomena that lead to a highly porous matrix with nanometer sized pores within and on the agglomerate surface.
In the preferred embodiment of the present invention, the process for producing a starting material in a granular form and in a nanoporous anhydrous state includes the step of drying the frozen droplets by vacuum sublimation to obtain freeze-dried granules of the starting material in a nanoporous anhydrous state.
In another embodiment of the present invention, a process for improving water-solubility and controlled release characteristics of a detergent material includes the steps of obtaining a detergent starting material in a form of a dispersion or solution in a sublimable solvent or mixtures of sublimable solvents, forming graded detergent droplets by atomization, freezing the graded detergent droplets in a freezing medium at a controlled freezing rate of at least 100xc2x0 C. per second to form frozen detergent droplets, and drying the frozen droplets by vacuum sublimation to obtain freeze-dried detergent granules of the detergent starting material in a nanoporous anhydrous state. The detergent starting material in dispersion or solution form has a viscosity suitable for atomization and formation of graded droplets. Desirably, the detergent starting material in the form of dispersion or solution has a viscosity in a range of from about 50 cP to about 125 cP at a solution temperature in a range of from about 60xc2x0 C. to about 91xc2x0 C. and at a shear rate in a range of from about 1000 secxe2x88x921 to about 10000 secxe2x88x921. Desirably, the graded detergent droplets have a uniform spherical shape and a size in a range from about 20 xcexcm to about 50 xcexcm and formed by atomization, preferably, by ultrasonic atomization means. In this embodiment, the controlled freezing rate is at least 200xc2x0 C. per second and the freeze-dried detergent granules in a nanoporous anhydrous state have uniformly sized pores having a pore size less than about 300 nanometers.
In another preferred embodiment of the present invention, a detergent composition comprising freeze-dried detergent granules in a nanoporous anhydrous state having uniformly sized pores having a pore size less than about 300 nanometers is disclosed.
The detergent composition may include surfactant systems such as anionic, nonionic, zwitterionic, ampholytic and cationic surfactant classes and compatible mixtures thereof. Detergent surfactants are described in U.S. Pat. No. 3,664,961, Norris, issued May 23, 1972, and in U.S. Pat. No. 3,919,678, Laughlin et al., issued Dec. 30, 1975, both of which are incorporated herein by reference. Cationic surfactants include those described in U.S. Pat. No. 4,222,905, Cockrell, issued Sep. 16, 1980, and in U.S. Pat. No. 4,239,659, Murphy, issued Dec. 16, 1980, both of which are also incorporated herein by reference.
Nonlimiting examples of surfactant systems include the conventional C11-C18 alkyl benzene sulfonates (xe2x80x9cLASxe2x80x9d) and primary, branched-chain and random C10-C20 alkyl sulfates (xe2x80x9cASxe2x80x9d), the C10-C18 secondary (2,3)alkyl sulfates of the formula CH3(CH2)x(CHOSO3xe2x88x92M+)CH3 and CH3(CH2)y(CHOSO3xe2x88x92M+)CH2CH3 where x and (y+1) are integers of at least about 7, preferably at least about 9, and M is a water-solubilizing cation, especially sodium, unsaturated sulfates such as oleyl sulfate, the C10-C18 alkyl alkoxy sulfates (xe2x80x9cAExSxe2x80x9d; especially EO 1-7 ethoxy sulfates), C10-C18 alkyl alkoxy carboxylates (especially the EO 1-5 ethoxycarboxylates), the C10-C18 glycerol ethers, the C10-C18 alkyl polyglycosides and their corresponding sulfated polyglycosides, and C12-C18 alpha-sulfonated fatty acid esters. If desired, the conventional nonionic and amphoteric surfactants such as the C12-C18 alkyl ethoxylates (xe2x80x9cAExe2x80x9d) including the so-called narrow peaked alkyl ethoxylates and C6-C12 alkyl phenol alkoxylates (especially ethoxylates and mixed ethoxy/propoxy), C12-C18 betaines and sulfobetaines (xe2x80x9csultainesxe2x80x9d), C10-C18 amine oxides, and the like, can also be included in the surfactant system. The C10-C18 N-alkyl polyhydroxy fatty acid amides can also be used. Typical examples include the C12-C18 N-methylglucamides. See WO 9,206,154. Other sugar-derived surfactants include the N-alkoxy polyhydroxy fatty acid amides, such as C10-C18 N-(3-methoxypropyl) glucamide. The N-propyl through N-hexyl C12-C18 glucamides can be used for low sudsing. C10-C20 conventional soaps may also be used. If high sudsing is desired, the branched-chain C10-C16 soaps may be used. Mixtures of anionic and nonionic surfactants are especially useful. Other conventional useful surfactants are listed in standard texts.
The detergent composition can, and preferably does, include a detergent builder. Builders are generally selected from the various water-soluble, alkali metal, ammonium or substituted ammonium phosphates, polyphosphates, phosphonates, polyphosphonates, carbonates, silicates, borates, polyhydroxy sulfonates, polyacetates, carboxylates, and polycarboxylates. Preferred are the alkali metal, especially sodium, salts of the above. Preferred for use herein are the phosphates, carbonates, silicates, C10-18 fatty acids, polycarboxylates, and mixtures thereof. More preferred are sodium tripolyphosphate, tetrasodium pyrophosphate, citrate, tartrate mono- and di-succinates, sodium silicate, and mixtures thereof (see below).
Specific examples of inorganic phosphate builders are sodium and potassium tripolyphosphate, pyrophosphate, polymeric metaphosphate having a degree of polymerization of from about 6 to 21, and orthophosphates. Examples of polyphosphonate builders are the sodium and potassium salts of ethylene diphosphonic acid, the sodium and potassium salts of ethane 1-hydroxy-1,1-diphosphonic acid and the sodium and potassium salts of ethane, 1,1,2-triphosphonic acid. Other phosphorus builder compounds are disclosed in U.S. Pat. Nos. 3,159,581; 3,213,030; 3,422,021; 3,422,137; 3,400,176 and 3,400,148, all of which are incorporated herein by reference.
Examples of nonphosphorus, inorganic builders are sodium and potassium carbonate, bicarbonate, sesquicarbonate, tetraborate decahydrate, and silicates having a weight ratio of SiO2 to alkali metal oxide of from about 0.5 to about 4.0, preferably from about 1.0 to about 2.4. Water-soluble, nonphosphorus organic builders useful herein include the various alkali metal, ammonium and substituted ammonium polyacetates, carboxylates, polycarboxylates and polyhydroxy sulfonates. Examples of polyacetate and polycarboxylate builders are the sodium, potassium, lithium, ammonium and substituted ammonium salts of ethylene diamine tetraacetic acid, nitrilotriacetic acid, oxydisuccinic acid, mellitic acid, benzene polycarboxylic acids, and citric acid.
Polymeric polycarboxylate builders are set forth in U.S. Pat. No. 3,308,067, Diehl, issued Mar. 7, 1967, the disclosure of which is incorporated herein by reference. Such materials include the water-soluble salts of homo- and copolymers of aliphatic carboxylic acids such as maleic acid, itaconic acid, mesaconic acid, fumaric acid, aconitic acid, citraconic acid and methylenemalonic acid. Some of these materials are useful as the water-soluble anionic polymer as hereinafter described, but only if in intimate admixture with the nonsoap anionic surfactant.
Other suitable polycarboxylates for use herein are the polyacetal carboxylates described in U.S. Pat. No. 4,144,226, issued Mar. 13, 1979 to Crutchfield et al., and U.S. Pat. No. 4,246,495, issued Mar. 27, 1979 to Crutchfield et al., both of which are incorporated herein by reference. These polyacetal carboxylates can be prepared by bringing together under polymerization conditions an ester of glyoxylic acid and a polymerization initiator. The resulting polyacetal carboxylate ester is then attached to chemically stable end groups to stabilize the polyacetal carboxylate against rapid depolymerization in alkaline solution, converted to the corresponding salt, and added to a detergent composition. Particularly preferred polycarboxylate builders are the ether carboxylate builder compositions comprising a combination of tartrate monosuccinate and tartrate disuccinate described in U.S. Pat. No. 4,663,071, Bush et al., issued May 5, 1987, the disclosure of which is incorporated herein by reference.
Water-soluble silicate solids represented by the formula SiO2.M2O, M being an alkali metal, and having a SiO2:M2O weight ratio of from about 0.5 to about 4.0, are useful salts in the detergent granules of the invention at levels of from about 2% to about 15% on an anhydrous weight basis, preferably from about 3% to about 8%. Anhydrous or hydrated particulate silicate can be utilized, as well.
Any number of additional ingredients can also be included as components in the granular detergent composition. These include other detergency builders, bleaches, bleach activators, suds boosters or suds suppressors, anti-tarnish and anti-corrosion agents, soil suspending agents, soil release agents, germicides, pH adjusting agents, nonbuilder alkalinity sources, chelating agents, smectite clays, enzymes, enzyme-stabilizing agents and perfumes. See U.S. Pat. No. 3,936,537, issued Feb. 3, 1976 to Baskerville, Jr. et al., incorporated herein by reference.
Bleaching agents and activators are described in U.S. Pat. No. 4,412,934, Chung et al., issued Nov. 1, 1983, and in U.S. Pat. No. 4,483,781, Hartman, issued Nov. 20, 1984, both of which are incorporated herein by reference. Chelating agents are also described in U.S. Pat. No. 4,663,071, Bush et al., from Column 17, line 54 through Column 18, line 68, incorporated herein by reference. Suds modifiers are also optional ingredients and are described in U.S. Pat. No. 3,933,672, issued Jan. 20, 1976 to Bartoletta et al., and U.S. Pat. No. 4,136,045, issued Jan. 23, 1979 to Gault et al., both incorporated herein by reference.
Suitable smectite clays for use herein are described in U.S. Pat. No. 4,762,645, Tucker et al., issued Aug. 9, 1988, Column 6, line 3 through Column 7, line 24, incorporated herein by reference. Suitable additional detergency builders for use herein are enumerated in the Baskerville patent, Column 13, line 54 through Column 16, line 16, and in U.S. Pat. No. 4,663,071, Bush et al., issued May 5, 1987, both incorporated herein by reference.